Modified zinc ferrite oxidative dehydrogenation catalysts

ABSTRACT

Improved oxidative dehydrogenation catalysts are prepared by modifying a zinc ferrite oxidative dehydrogenation catalyst with magnesium oxide. The resulting catalyst compositions exhibit higher conversions and yields.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for dehydrogenating hydrocarbons.More particularly, this invention relates to the oxidativedehydrogenation of organic compounds in the presence of modified zincferrite catalyst compositions.

2. Description of the Prior Art

Oxidative dehydrogenation processes wherein zinc ferrite catalystcompositions have been employed to convert saturated and/or unsaturatedhydrocarbons to more highly unsaturated hydrocarbons through removal ofhydrogen from such hydrocarbons are known in the art. See, for example,U.S. Pat. No. 3,303,235. However, such catalyst compositions do notretain their good initial activity and deteriorate rapidly under thereaction conditions of the oxidative dehydrogenation process. Suchdeterioration necessitates the frequent and uneconomic regeneration ofthe catalyst composition.

Accordingly, it is an object of the present invention to providecatalyst compositions which, when employed in oxidative dehydrogenationprocesses, effect high conversions at high selectivities to the desiredproduct.

It is another object of the present invention to provide more stableand, hence, longer-lived catalyst compositions than heretofore employedin oxidative dehydrogenation processes.

SUMMARY OF THE INVENTION

In accordance with the present invention, a process is provided for theoxidative dehydrogenation of organic compounds which comprisescontacting an organic compound having from about 2 to about 20 carbonatoms and oxygen in the presence of a zinc ferrite catalyst compositionadditionally containing magnesium oxide as a catalyst modifier, in anamount of from about 0.1 to about 10 wt.% based on the weight of thezinc ferrite composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the process of the instant invention, certain organiccompounds are dehydrogenated to less saturated compounds of the samecarbon number at elevated temperature in the presence of oxygen and thecatalysts of the instant invention.

The process of this invention may be applied to the dehydrogenation of awide variety of organic compounds. Such compounds normally will containfrom 2 to 20 carbon atoms, at least one ##STR1## grouping, a boilingpoint below about 350° C., and such compounds may contain otherelements, in addition to carbon and hydrogen such as oxygen, halogens,nitrogen and sulfur.

Among the types of organic compounds which may be dehydrogenated bymeans of the process of this invention are nitriles, amines, alkylhalides, ethers, esters, aldehydes, ketones, alcohols, acids, alkylaromatic compounds, alkyl heterocyclic compounds, cycloalkanes, alkanes,alkenes, and the like. Illustrative dehydrogenations which may becarried out by the process of this invention include propionitrile toacrylonitrile; propionaldehyde to acrolein; ethylchloride to vinylchloride; methyl isobutyrate to methyl methacrylate; 2 or 3chlorobutene-1 or 2,3-dichlorobutane to chloroprene; ethyl pyridine tovinyl pyridine; ethylbenzene to styrene; isopropylbenzene to α-methylstyrene; ethylcyclohexane to styrene; cyclohexane to benzene; ethane toethylene or acetylene; propane to propylene, methylacetylene, allene, orbenzene; isobutane to isobutylene; n-butane to butene and butadiene;n-butene to butadiene-1,3 and vinyl acetylene; methyl butene toisoprene; cyclopentane to cyclopentene and cyclopentadiene-1,3; n-octaneto ethyl benzene and orthoxylene; monomethylheptanes to xylenes; ethylacetate to vinyl acetate; methyl isobutyrate to methyl methacrylate;2,4,4-trimethylpentane to xylenes; and the like. Other materials whichare dehydrogenated by the process of this invention include ethyltoluene, alkyl chlorobenzenes, ethyl naphthalene, isobutyronitrile,propyl chloride, isobutyl chloride, ethyl fluoride, ethyl bromide,n-pentyl iodide, ethyl dichloride, 1,3-dichlorobutane,1,4-dichlorobutane, the chlorofluoroethanes, methyl pentane, methylethylketone, diethyl ketone, n-butyl alcohol, methyl propionate, and thelike.

The catalyst compositions of this invention are also useful for theformation of new carbon-to-carbon bonds by the removal of hydrogenatoms. For example, acyclic compounds having from 6 to about 16 carbonatoms and no quaternary carbon atoms are converted to cyclic compoundsof greater degree of unsaturation, e.g., n-hexene to benzene. Also,propene is converted to diallyl.

The preferred compounds which are dehydrogenated by the process of thisinvention are hydrocarbons having from about 3 to about 12 carbon atoms,including alkanes, alkenes, cycloalkanes, cycloalkenes, and aromaticcompounds having one or two alkyl side chains of from 2 to 3 carbonatoms. A preferred hydrocarbon feed for the process of this inventionwould be selected from the group of n-butane, n-butene, pentane orpentene including all isomers and mixtures thereof, the methyl butenes,the hexenes, ethyl benzene, etc. and mixtures thereof. Especiallypreferred are acyclic hydrocarbons having 4 to 5 contiguousnon-quaternary carbon atoms, such as butane, the butenes, the methylbutenes and mixtures thereof.

In the instant process, the organic compound is dehydrogenated in thepresence of oxygen. Oxygen may be fed to the reaction zone as pureoxygen, air, oxygen-enriched air, oxygen mixed with a diluent, and soforth. Oxygen in the desired amount may be added in the feed to thedehydrogenation zone and oxygen may also be added in increments to thedehydrogenation zone. The oxygen may be supplied in a cyclic manner suchas described in U.S. Pat. No. 3,420,911.

The amount of oxygen employed in the oxidative dehydrogenation processwill vary depending upon the particular compound being dehydrogenated,the number of hydrogen atoms being removed, and the conversion level.For example, in dehydrogenating butane to butene, less oxygen isgenerally employed than if the reaction were carried out to producebutadiene. Normally oxygen will be supplied in the dehydrogenation zonein an amount from about 0.2 to about 1.5, and preferably from about 0.3to about 1.2 mols of oxygen per mol of H₂ being liberated from theorganic compound. Expressed in terms of the organic compound beingdehydrogenated, the oxygen is supplied in an amount of from about 0.2 to2.0 mols per mol of organic compound to be dehydrogenated with apreferred range of from about 0.25 to 1.5 mols of oxygen per mol oforganic compound.

Preferably, the reaction mixture contains a quantity of steam or adiluent such as nitrogen. These gases serve to reduce the partialpressure of the organic compound; however, the functions of steam in thereaction are several fold in that the steam does not act merely as adiluent. Whenever steam is employed in the process of the instantinvention, it is employed in an amount generally of from about 2 toabout 40 mols of steam per mol of organic compound to be dehydrogenated,with an amount of from about 3 to about 35 mols of steam per mol oforganic compound to be hydrogenated being preferred. Especiallypreferred are amounts of from about 5 to about 30 mols of steam per molof organic compound to be dehydrogenated. Whenever a diluent is employedinstead of steam, such diluents generally may be used in the samequantities as specified for steam.

In one modification of this invention, halogen is present in thereaction gases. The presence of halogen in the dehydrogenation zone isparticularly effective whenever the compound to be dehydrogenated is asaturated hydrocarbon. Whenever halogen is employed in thedehydrogenation zone, it is provided as elemental halogen or a compoundof halogen which liberates halogen under the conditions of thedehydrogenation reaction. Suitable sources of halogen include hydrogeniodide, hydrogen bromide and hydrogen chloride; aliphatic halides suchas ethyl iodide, methyl bromide, methyl chloride, and 1,2-dibromoethane;cycloaliphatic halides; ammonium iodide, ammonium bromide, ammoniumchloride, sulfuryl chloride; metal halides including molten halides; andthe like. The halogen also may be liberated partially or entirely by asolid source as disclosed in the process of U.S. Pat. No. 3,130,241issued Apr. 21, 1964. Mixtures of various sources of halogen may beused. Whenever employed in the process of the instant invention, theamount of halogen employed (calculated as elemental halogen) is fromabout 0.0001 to about 1.0 mols of halogen per mol of the organiccompound to be dehydrogenated with an amount of from about 0.01 to about0.5 mols of halogen per mol of organic compound being preferred.

The catalyst compositions useful in the present invention include zincferrites containing, as the active components thereof, zinc, iron andoxygen in combination as hereinafter described and additionallycontaining free magnesium oxide as a modifier.

The zinc ferrite constituents of the instant catalyst compositionscomprise zinc ferrite of the empirical formula Zn_(x) Fe_(y) O_(z),wherein x will be from about 0.1 to 2, inclusive, and y can be in therange of about 0.3 to 12, inclusive, and z will vary depending upon thenumber of oxygen vacancies, but will usually be within the range ofabout 3 to 18, inclusive. Especially preferred are zinc ferritecompositions wherein the ratio of y to x is from about 2:1 to about 5:1.Although the modified zinc ferrite catalyst may be broadly defined ascontaining crystalline structures of iron, oxygen and zinc, certaintypes of catalysts are preferred. Zinc ferrite formation may beaccomplished by reacting an active compound of iron with an activecompound of zinc. By the term active compound is meant a compound whichis reactive under the conditions hereinafter described to form theferrite. The active compounds are suitably oxides or compounds which areconverted to oxides during the formation of the ferrite, such as organicand inorganic salts or hydroxides. Active compounds of iron and zincinclude the nitrates, hydroxides, hydrates, oxalates, carbonates,acetates, formates, halides, oxides, etc. For example, zinc carbonatemay be reacted with iron oxide hydrates to form zinc ferrite. Salts ofthe desired metals may be co-precipitated and the precipitate heated toform the ferrite. Desired ferrites may be obtained by conducting thereaction to form the ferrite at relatively low temperatures, that is, attemperatures lower than some of the very high temperatures used for theformation of some of the semiconductor applications. Good results havebeen obtained by heating the ingredients to a temperature high enough toproduce the zinc ferrite, but at conditions no more severe thanequivalent to heating to 850° C. for 90 minutes in air. Generally, themaximum temperature will be less than 700° C. and preferably about 650°C. Methods for preparing zinc ferrite catalyst compositions suitable foruse in the process of this invention are disclosed in U.S. Pat. Nos.3,270,080; 3,284,536; 3,303,234-6; 3,303,238; 3,308,182; 3,334,152;3,420,912; 3,440,229; 3,342,890 and 3,450,787.

As is apparent from the empirical formula presented herein for zincferrite, the ratio of iron to zinc in such ferrite mixtures is notrestricted to the stoichiometric ratios as would be present in thesimple compound zinc ferrite. In the catalyst compositions of theinstant invention, there is present zinc ferrite compound as well as oneor more oxides of the constituent cations. For example, if the activecompounds are employed such that in the empirical formula y is about 3and x is 1, the catalyst composition formed therefrom will contain ironoxide in addition to the zinc ferrite formed. Similarly, the zincferrite precursor composition may comprise an excess of zinc over thestoichiometric amount to form the ferrite, in which case the resultingcatalyst will contain zinc oxide in addition to the zinc ferrite formed.

The preferred zinc ferrite catalyst compositions of the instantinvention are those having a face centered cubic structure. However, thezinc ferrites of the instant invention will not be present in the mosthighly oriented crystalline structure because it has been found thatsuperior results may be obtained with catalysts wherein the zinc ferriteis relatively disordered. Such catalyst compositions may be obtained byconducting the reaction to form the zinc ferrite at relatively lowtemperatures as described herein.

The zinc ferrite catalyst compositions of the present invention can beidentified by their characteristic X-ray diffraction patterns. Thepreferred catalyst compositions will generally have X-ray diffractionpeaks at d-spacings within or about 4.83 to 4.89; 2.95 to 3.01; 2.51 to2.57; 2.40 to 2.46; 2.08 to 2.14; 1.69 to 1.75; 1.59 to 1.65; and 1.46to 1.52, with the most intense peak being between 2.51 to 2.57.Particulaly preferred catalysts will have d-spacings within or about4.81 to 4.88; 2.96 to 3.00; 2.52 to 2.56; 2.41 to 2.45; 2.09 to 2.13;1.70 to 1.74; 1.60 to 1.64; and 1.47 to 1.51, with the most intense peakfalling within or about 2.52 to 2.56. These X-ray determinations aresuitably run with a cobalt tube.

The magnesium oxide catalyst modifier of the instant invention can beemployed in the form of magnesium oxide itself or a magnesium compoundwhich will be converted to magnesium oxide under the reaction conditionsset forth herein. Particularly effective are inorganic magnesiumcompounds such as the oxides and salts, including the phosphates,phosphites, sulfites, thiocyanates, thiosulfates, and the like.Specially preferred are magnesium oxide and magnesium carbonate.

The magnesium oxide or magnesium oxide precursor catalyst modifier maybe added to the zinc ferrite by any suitable method. The modifier may beincorporated into the catalyst precursor mixture or may be added afterthe zinc ferrite has been formed. If the catalyst support or carrier isemployed, one convenient method is to form a slurry of the modifier withthe zinc ferrite prior to coating on the support. Although aqueousmediums will generally be employed when coating a support with thecatalyst constituents, it is contemplated that non-aqueous systems canalso be employed, if desired, in the preparation of the catalyst.Another suitable method for incorporating the modifier into the zincferrite composition is by dry-mixing the components.

The magnesium oxide modifier is present in the zinc ferrite catalystcomposition in a catalytic promoting amount. Generally, a catalyticpromoting amount of magnesium oxide will be not more than about 10% byweight, based on the total weight of the zinc ferrite compositionpresent. Amounts of magnesium oxide of from about 0.1 to 10% aresatisfactory, with amounts of from about 1.0 to about 5.0%, based on theweight of zinc ferrite composition being preferred.

In an even more preferred catalyst composition according to the presentinvention, manganese oxide is present as a modifier in addition tomagnesium oxide.

The manganese oxide catalyst modifier of the instant invention can beemployed in the form of manganese oxide itself or a manganese compoundwhich will be converted to manganese oxide under the reaction conditionsset forth herein. Particularly effective are inorganic manganesecompounds such as the oxides and salts, including the phosphates,sulfates, phosphites, sulfites, silicates, thiocyanates, thiosulfates,and the like. Specially preferred are manganese oxide and manganesecarbonate.

The manganese oxide or manganese oxide precursor catalyst modifier maybe added to the zinc ferrite by any suitable method in the same manneras the magnesium oxide or precursor.

The manganese oxide modifier is present in the zinc ferrite catalystcomposition in a catalytic promoting amount. Generally, a catalyticpromoting amount of manganese oxide will be not more than about 10% byweight, based on the total weight of the zinc ferrite compositionpresent. Amounts of manganese oxide of from about 0.1 to 10% aresatisfactory, with amounts of from about 1.0 to about 5.0%, based on theweight zinc ferrite composition being preferred.

Catalyst binding agents for fillers not mentioned herein may also beused, but these will not ordinarily exceed about 50 percent or 75percent by weight of the catalytic surface, and the described catalyticcompositions will preferably constitute the main active constituent.These other binding agents and fillers will preferably be essentiallyinert. Preferred catalysts are those that have as a catalytic surfaceexposed to the reaction gases at least 25 or preferably 50 weightpercent of the defined catalytic surface. The catalytic surface may beintroduced as such or it may be deposited on a carrier by methods knownin the art such as by preparing an aqueous solution or dispersion of acatalytic material and mixing the carrier with the solution ordispersion until the active ingredients are coated on the carrier. If acarrier is utilized, very useful carriers are silicon carbide, aluminumoxide, pumice, and the like. Other known catalyst carriers may beemployed. When carriers are used, the amount of catalyst on the carrierwill suitably be between about 5 to 75 weight percent of the totalweight of the active catalytic material plus carrier. Another method forintroducing the required surface is to utilize as a reactor a smalldiameter tube wherein the tube wall is catalytic or is coated withcatalytic material. Other methods may be utilized to introduce thecatalytic surface such as by the use of rods, wires, mesh, or shreds,and the like, of catalytic material. The catalytic surface described isthe surface which is exposed in the dehydrogenation zone to the reactiongases, that is, e.g., if a catalyst carrier is used, the compositiondescribed as a catalyst refers to the composition of the surface and notto the total composition of the surface coating plus carrier.

The catalyst compositions of the instant invention may be activatedprior to use by treatment with a reducing gas, such as, for example,hydrogen or hydrocarbons. For example, the reduction may be effectedwith hydrogen at a temperature of from about 500° F. to about 1,000° F.,with temperatures of from about 650° F. to about 850° F. beingpreferred. The time required for reduction will be dependent upon thetemperature selected for the reducing step and will generally be fromabout ten minutes to about two hours.

The catalyst compositions of this invention may also comprise additives,such as disclosed in U.S. Pat. No. 3,270,080 and U.S. Pat. No.3,303,238. Phosphorus, silicon, boron, sulfur, or mixtures thereof, areexamples of additives. Excellent catalysts may contain less than 5 wt.%,and preferably less than 2 wt.%, of sodium or potassium in the catalystcomposition. The catalyst compositions of this invention may alsocomprise other metallic promoters as are well-known in the art.

The Reaction Conditions.

The temperatures for the dehydrogenation reaction will depend upon thecompound being dehydrogenated and the desired level of conversion.Generally, temperatures of from about 500° F. to about 1,200° F. aresatisfactory with temperatures of from about 650° F. to about 1,100° F.being preferred.

The process of the instant invention is carried out at atmosphericpressure, superatmospheric pressure or at subatmospheric pressure. Thereaction pressure will normally be about or in excess of atmosphericpressure, although subatmospheric pressure may also desirably be used.Generally, the total pressure will be between about 2 p.s.i.a. and about125 p.s.i.a., with a total pressure of from 4 p.s.i.a. to about 75p.s.i.a. being preferred. Excellent results are obtained at aboutatmospheric pressure.

The gaseous reactants may be conducted through the dehydrogenation zoneat a fairly wide range of flow rates. The optimum flow rate will dependupon such variables as the temperature and pressure of reaction, and theparticular hydrocarbon being dehydrogenated. Desirable flow rates may beestablished by one skilled in the art. Generally, the flow rates will bewithin the range of about 0.10 to 15 liquid volumes of the organiccompound to be dehydrogenated per volume of dehydrogenation zonecontaining catalyst per hour (referred to as LHSV). Usually, the LHSVwill be between 0.15 and about 5.0.

In calculating space velocities, the volume of a fixed beddehydrogenation zone containing catalyst is that original void volume ofreactor space containing catalyst. The gaseous hourly space velocity(GHSV) is the volume of the hydrocarbon to be dehydrogenated, in theform of vapor calculated under standard conditions of 25° C. and 760 mm.of mercury, per volume of reactor space containing catalyst per hour.Generally, the GHSV will be between about 25 and 6400, and excellentresults are obtained between about 38 and 3800. Suitable contact timesare, for example, from about 0.001 or higher to about 5 or 10 seconds,with particularly good results being obtained between 0.01 and 3seconds. The contact time is the calculated dwell time of the reactionmixture in the reaction zone, assuming the mols of product mixture areequivalent to the mols of feed mixture. For the purpose of calculationof residence times, the reaction zone is the portion of the reactorcontaining catalyst.

The process of this invention is suitably deployed with a fixed catalystbed or a moving catalyst bed, such as a fluidized catalyst bed in thedehydrogenation zone.

The following examples are illustrative only of the invention and arenot intended to limit the invention. All percentages are weight percentunless specified otherwise. All conversions, selectivities and yieldsare expressed in mol percent of the designated feed.

EXAMPLE I A. Preparation of a Magnesium-Modified Zinc-Ferrite CatalystComposition.

To approximately 35 liters of distilled water were added 6,570 g. of 87%ferric oxide, 3,733 g. zinc carbonate and 51.6 g. zinc chloride to forma slurry. By emission spectra analysis, the zinc carbonate (NaftoneF-5637) was shown to contain 1.0% magnesium and 49.0% zinc, as metal.This corresponds to a magnesium carbonate content of approximately 3.6wt.% of the zinc carbonate-magnesium carbonate mixture. The slurry wasthoroughly mixed for five hours after whch time it was dewatered byfiltering and the filter cake was dried in an oven at 260° F. for 12hours. The dried filter cake thus obtained was granulated and blended ina Patterson-Kelly blender with enough water to form moist granules. Thegranules were then dried at 260° F. for 12 hours. After drying, thegranules were calcined at 1,200° F. for 14 minutes in the presence ofoxygen to form a zinc ferrite-magnesium oxide-containing catalystcomposition. The catalyst composition was analyzed by X-ray diffractionand found to contain zinc ferrite, magnesium oxide, 9 wt.% free oruncombined ferric oxide and 2 wt.% zinc oxide.

The dry, modified ferrite-containing powder was then placed in aPatterson-Kelly blender and mixed with an aqueous solution containing 2wt.% polyvinyl alcohol and 7 wt.% phosphoric acid to give a damp powderwith a moisture content of approximatly 28 wt.%. The damp ferrite powderwas then pelletized (1/16-inch pellets) in a California pellet mill.

B. A total of 125 cc. of the pelleted catalyst composition producedaccording to the procedure of Part A of this example was used todehydrogenate butene-2 to butadiene-1,3 using a 25 mm. OD glass reactorapproximately 13 inches long in the heated reactor section. Butene-2 wasfed together with oxygen (as air) and steam over a fixed catalyst bed.The effluent gases from the reactor section were passed through a coldwater condenser to remove most of the steam and samples of the effluentgas were withdrawn with a syringe at the exit from the condenser andwere analyzed in a Perkin-Elmer vapor chromatograph. The butene-2 usedwas CP grade (99.0 mol percent minimum) and the oxygen was commercialgrade purity (99.5 mol percent).

Prior to use, the catalyst composition was pretreated by reduction for 3hours at 850° F.-1,050° F. in the presence of a fluent gas containingsteam and a trickle of nitrogen. Steam was employed at a GHSV ofapproximately 12 times the GHSV at which the butene-2 was to be passedover the catalyst during the oxidative dehydrogenation. After thereduction step, butene-2 was fed to the reactor at an LHSV of 1.5 alongwith air and steam. Air was introduced to the reactor at a rate suchthat the oxygen/hydrocarbon mol ratio was 0.55/1 and steam wasintroduced at a steam/hydrocarbon mol ratio of 18/1. The conversion ofbutene-2 was 68.3 mol % and the selectivity to butadiene-1,3 was 95.7mol %. The overall yield of butadiene-1,3 was 65.7 mol %.

EXAMPLE II

A zinc ferrite catalyst composition was prepared according to the methodExample IA except that no magnesium was present in the catalystprecursor mixture. The resulting catalyst composition was pelletized(1/16-inch pellets) and 125 cc. of the catalyst was reduced and employedto dehydrogenate butene-2 according to the method of Example IB. At anoxygen/hydrocarbon mol ratio of 0.55/1 and a steam hydrocarbon mol ratioof 20/1, the conversion of butene-2 was 65.8 mol % with a selectivity tobutadiene-1,3 of 94.3 mol %. The overall yield of butadiene-1,3 was 62.0mol %.

The above data demonstrate that the incorporation of magnesium into thezinc ferrite catalyst composition as shown in Example I provides avastly superior catalyst composition. With the magnesium-modifiedcatalyst, the conversion level of butene-2 was 2.5 mol % higher at a 1.4mol % higher selectivity and the yield was 3.7 mol % higher than for theunmodified zinc ferrite catalyst composition.

EXAMPLE III

To further illustrate the promotional effect of magnesium in the zincferrite catalyst compositions of this invention, two manganese-modifiedzinc ferrites were prepared with the following general composition: 86.2g. ferric oxide (YLO 1788, C. Pfizer & Co.), 47.3 g. zinc carbonate, 3.0g. zinc chloride and 7.85 g. manganese carbonate. In one catalystcomposition, designated catalyst A, the zinc carbonate employed was thatemployed in the procedure of Example I (Naftone F-5637) ) and magnesium.The other catalyst composition, designated catalyst B, employed a zinccarbonate free from magnesium.

Catalysts A and B were prepared as follows: the above weights ofmaterials were combined with 750 cc. of demineralized water in a 1-quartWaring Blender and blended for 20 minutes. The slurry was then pouredinto a Pyrex dish and dried overnight at 110° C. The dried cake wascrushed and calcined at 1,125° F. for 15 minutes with air flow over thematerial during the calcination.

The calcined material was then coated onto a support material by placing125 g. of3-5 mesh AMC, 67.3 g. of the calcined ferrite composition, 2.47g. of phosphoric acid (85%), and approximately 200 cc. of water in alaboratory pill coater. The coated catalysts were then pretreated byreduction for 2 hours at 950° F. in the presence of a fluent gasconsisting of steam and hydrogen. Steam was passed over the catalyst ata GHSV of 10 times the hydrocarbon feed rate to be employed and thehydrogen rate was 400 cc./min. The two catalysts were then employed tooxidatively dehydrogenate butene-2 at an LHSV of 1.5 in the presence ofair and steam. The data from the experimental runs are recorded in thefollowing table:

                                      Table 1                                     __________________________________________________________________________         Hours on                                                                            O.sub.2 /Steam/HC                                                                     Conversion                                                                          Selectivity                                                                          Yield                                                                             Maximum                                   Catalyst                                                                           Steam Mol Ratio                                                                             Mol % Mol %  Mol %                                                                             Temp. ° F.                         __________________________________________________________________________    A    435.25                                                                              .56/15/1                                                                              74.8  95.4   71.3                                                                              900                                       A    700   .61/15/1                                                                              77.4  94.6   73.2                                                                              912                                       B    336   .50/20/1                                                                              66.7  95.5   63.7                                                                              922                                       B    737.75                                                                              .56/15/1                                                                              71.1  94.6   67.3                                                                              886                                       __________________________________________________________________________

The above data demonstrate that the incorporation of magnesium into themodified zinc ferrite catalyst composition results in a superiorcatalyst. With the magnesium-modified catalyst, the conversion level ofbutene-2 is from 6.3 to 8.1 mol % higher at comparable selectivities toproduce a yield of from 5.9 to 7.6 mol % higher than for the zincferrite composition containing no magnesium.

From the foregoing description and Examples of this invention, those ofordinary skill in the art may make many modifications and variationstherefrom without departing from the scope of the invention ashereinafter claimed.

We claim:
 1. A catalyst composition suitable for oxidativedehydrogenation of organic compounds consisting essentially of a zincferrite composition having the empirical formula

    Zn.sub.x Fe.sub.y O.sub.z

wherein x is from about 0.1 to 2, y is from about 0.3 to about 12 and zis from about 3 to about 18 and a promoter of magnesium oxide in anamount of from about 0.1 to about 10 weight percent and manganese oxidein an amount of about 0.1 to about 10 wt. percent based on the weight ofthe zinc ferrite composition.
 2. The composition according to claim 1wherein the amount of manganese oxide is 1.0 to 5.0 weight %.
 3. Thecomposition according to claim 2 wherein the amount of magnesium oxideis 0.1 to 5.0 weight %.